docstr: Shuts down workers and releases resources.
  
  :return:
docstr_tok: ["Shuts","down","workers","and","releases","resources",".",":","return",":"]
code: def shutdown(self, force: bool = False):
      """
      Shuts down workers and releases resources.
  
      :return:
      """
      if not force:
          cleanup = [
              worker.shutdown.remote() for worker in self.remote_workers
          ]
          try:
              ray.get(cleanup)
              [
                  worker.__ray_terminate__.remote()
                  for worker in self.remote_workers
              ]
          except RayActorError:
              logger.warning(
                  "Failed to shutdown gracefully, forcing a shutdown."
              )
  
              for worker in self.remote_workers:
                  logger.warning("Killing worker {}.".format(worker))
                  ray.kill(worker)
      else:
          for worker in self.remote_workers:
              logger.debug("Killing worker {}.".format(worker))
              ray.kill(worker)
  
      self.remote_workers = []
  
imports: from bigdl.orca.learn.ray_estimator import BaseEstimator
  from bigdl.orca.ray import OrcaRayContext
  from bigdl.orca.data.file import enable_multi_fs_save, enable_multi_fs_load
  import io
  import torch
  import ray
  from ray.exceptions import RayActorError
  from abc import abstractmethod, ABCMeta
  from bigdl.orca.learn.pytorch.utils import find_free_port, check_for_failure
  from bigdl.orca.learn.utils import get_driver_node_ip
  from bigdl.dllib.utils.log4Error import invalidInputError, logging
  from typing import Dict
label_desc: Use image node_id 14 for calling the BaseRayEstimator obj's underlying member method code with example usage: obj.shutdown(force) without return types